In international application PCT/AU95/00667 there is disclosed an arrangement for lining a passageway created by a mining head as it advances through an underground formation. The mining head excavates material as it advances, thereby creating the passageway. The excavated material is conveyed to ground surface by a pipe string extending along the passageway from the mining head. The pipe string is also utilised to deliver services required by the mining head during performance of the mining operation. The pipe string progressively enters the passageway and advances therealong with the mining head. It also retreats with the mining head. Because the pipe string moves within the passageway, it is important that the passageway does not collapse upon the pipe string. The passageway is therefore progressively lined as it is created. The lining is by way of a shroud which is assembled and inflated to provide a generally cylindrical load-bearing liner.
The lining arrangement is particularly suitable for use with a mining head of the type disclosed in international application PCT/AU96/00106. Such a mining head, however, presents a generally rectangular front profile and so the passageway that it excavates is correspondingly rectangular in cross-section. Thus, there is disconformity between the generally rectangular cross-sectional shape of the passageway and the generally circular cross-sectional shape of the liner. This provides a vacant space between the periphery of the passageway and the periphery of the liner into which some of the material bounding the passageway can collapse.
Further, material which has collapsed into the space about the liner behind the mining head must be extracted in order for the mining head to be reversed. This can be done by extracting the collapsed material from the region behind the mining head and delivering it to the region in front of the mining head, thus continually providing space behind the mining head into which the mining head can reverse. One way of extracting the collapsed material behind the mining head and delivering it to the region in front of the mining head is to pump the material through the mining head, as disclosed in international application PCT/AU96/00106. This requires a pumping system within the mining head, which adds to the cost and complexity of the mining head and also occupies space within the mining head which could otherwise be used for other purposes. It is against this background that the present invention has been developed.
The above discussion of the background to the invention is intended to facilitate an understanding of the present invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge in Australia as at the priority date of the application.